The present invention relates to a semiconductor manufacturing technique that reduces the cost and complexity of producing multiple undercut profiles in the same material. For example, the present invention provides a simplified etch process capable of generating two different undercut profiles in the same material, such as silicon dioxide or the like, using a single lithographic step during the manufacture of flat-panel field emission display (FED) devices.
Conventional semiconductor techniques commonly utilize lithographic techniques to selectively place a pattern on a work piece during manufacture. For example, lithography may be used to apply a resist pattern over a layer of material such as silicon dioxide. An etching process then removes portions of the silicon dioxide that remain exposed after the photoresist pattern is printed over the silicon dioxide layer. Such an etching process allows a manufacturer to obtain a desired structure in the underlying material. The photoresist pattern is typically removed after etching and the work piece may be processed further by the deposition of additional material layers and further selective etchings. Mechanical operations such as chemical-mechanical planarization (CMP) and other processes may also be used in the manufacturing process.
One difficulty that has been encountered in prior manufacturing techniques is based on the requirement that the various layers of the semiconductor device be aligned with a relatively high degree of alignment accuracy. Unfortunately, lithographic printing techniques may be somewhat limited in alignment accuracy and resolution. For example, one resist pattern may be slightly offset relative to the underlying work piece. If a subsequent resist layer is also offset, possibly in a direction different from the first offset direction then a defect may result, lowering the effective yield of the manufacturing process. Similarly, the resolution of the printing process might not allow for fine detail that would permit certain structures to be obtained. Thus, it may be necessary to introduce a relatively large “margin of error” into the manufacturing process by producing features that are large enough to accommodate misalignments. Of course, this limits the degree of miniaturization that may be achieved in the manufacturing operation.
Each photolithographic/etching step entails the expenditure of time and resources, adding to the costs of manufacture. Moreover, each photolithographic/etching step carries with it the possibility of errors or defects and, consequently, potentially reduced yields. Thus, from the standpoint of size, cost and yield, it is desirable to minimize the number of photolithographic steps performed during the manufacturing operation.
It is a primary objective of the present invention to provide a simplified etch process that avoids difficulties encountered in prior art manufacturing techniques, and is capable of producing two different undercut profiles in a work piece using a single lithographic step. The present invention may find application, for example, in the manufacture of flat-panel field emission displays (FEDs). However, the invention is not limited to FEDs and may be used in connection with manufacturing processes for other devices such as micromachines that may require undercut structures within a base material.